     :contributors "Mitwirkende"
     :enclosures "Hörbuchbeilagen"
     :end "Ende des Buches"
-    :title_creator_fmt "%s von %s"}
+    :title_creator_fmt "%s von %s"
+    :unknown_title "Unbekannter Titel"}
    :en
    {:about "About this DAISY book"
     :bib "Bibliographic information"

(def ^:private formatter (f/formatters :date))
(defn- format-date [date] (when date (f/unparse formatter (from-date date))))

(defn default-book
  "Return an default book sexp"
  [title creator language]
  (let [t (partial translate language)]
    [:book
     [:frontmatter
      [:doctitle (format (t :title_creator_fmt) title creator)]
      [:docauthor creator]]
     [:bodymatter
      [:level1 [:h1] [:p]]]]))

(defn periodical
  "Return an default periodical sexp"

    :contributors "Contributors"
    :enclosures "Talking book enclosures"
    :end "End of book"
    :title_creator_fmt "%s by %s"
    :unknown_title "Unknown title"}})

(def ^:private doctype
  (str
